Messages in this thread | | | From | Nikita Danilov <> | Date | Mon, 24 Jul 2006 10:45:45 +0400 | Subject | Re: what is necessary for directory hard links |
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Joshua Hudson writes: > On 7/22/06, Bodo Eggert <7eggert@elstempel.de> wrote: > > Horst H. von Brand <vonbrand@inf.utfsm.cl> wrote: > > > > > Joshua Hudson <joshudson@gmail.com> wrote: > > >> This patch is the sum total of all that I had to change in the kernel > > >> VFS layer to support hard links to directories > > > > > > Can't be done, as it creates the possibility of loops. > > > > Don't do that then? > Exactly. > > > > Detecting unconnected subgraphs uses a /lot/ of memory; and much worse, you > > > have to stop (almost) all filesystem activity while doing it. > I know. > > I just decided the price is worth it. > > In my filesystem, any attempt to create a loop of hard links > is detected and cancelled.
Can you elaborate a bit on this exciting mechanism? Obviously an ability to efficiently detect loops would be a break-through in a reference-counted garbage collection, somehow missed for last 40 years. :-)
> Unlinking a directory requires it > to be empty if the last link is being removed. "." and ".." > links are counted separately from real links, so that is easy.
Nikita.
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